1. Field of the Invention
The present invention relates, generally, to a method for monitoring optical communication equipment and, more specifically, to a monitoring method wherein both the levels of the total signals on a plurality of optical fibers are checked and the signal qualities of individual communication channels respectively transmitted on one fiber are monitored in order to establish a monitoring algorithm by which critical channels are monitored more intensively than reliable ones.
2. Description of the Prior Art
Monitoring problems in an optical transport network are described, for example, in "IEEE Journal on Selected Areas in Communications", Vol. 14, No. 5, June 1996, pp. 914-922. At present, optical communication systems (All Optical Networks/Photonic Transport Networks) are in the standardization phase. This entails an orientation to the existing standards for synchronous communication systems (SDH-Synchronous Digital Hierarchy; SONET--Synchronous Optical Network) in the defining of the characteristic structural features; the aim being a maximum structural similarity of the network structures. In purely optical add/drop multiplexers or cross-connectors, which may be employed medium-term, there are approximately 30 to 300 optical channels to be wired to one another. As is already the case in known synchronous communication systems, rather high requirements are placed upon the operating reliability in the purely optical systems. However, these can be guaranteed only if the optical channels are continuously individually monitored with respect to their signal quality and if substitute transmission paths are immediately available in case of error.
The time-span between the arising of an error and the completion of the substitution process is 50 ms in synchronous networks. In order to be able to integrate the new purely optical communication systems into the overall communication network without complications, these reaction times must be maintained or even shortened. However, a monitoring of all the optical communication channels using conventional transmission equipment is associated with prohibitive technical outlay and, thus, with prohibitive costs.
It is therefore an object of the present invention to offer a method for monitoring optical communication systems having a plurality of optical channels, wherein the method can be realized cost-effectively.